AnimationController.dispose() called more than once

[JagandeepBrar]

Describe the bug
When using TyperAnimatedTextKit in a widget that will eventually get removed, an error is shown because the animation controller is attempted to be destroyed multiple times.

To Reproduce
In my use case, I have a FutureBuilder that calls a "Loading" widget (Which contains a TyperAnimatedTextKit), and once the data is loaded FutureBuilder removes the loading widget and replaces it with the content widgets.

Expected behavior
It still works, and it doesn't cause a crash but it prints out to the command line each time (as well as logs internally in my logger).

Screenshots

AnimationController#54de2(⏭ 1.000; paused; DISPOSED)] [Exception: AnimationController.dispose() called more than once.
A given AnimationController cannot be disposed more than once.
The following AnimationController object was disposed multiple times:
  AnimationController#54de2(⏭ 1.000; paused; DISPOSED)] [LogLevel.FATAL] [March 08, 2020 - 06:31:29 PM] [#0      AnimationController.dispose.<anonymous closure> 
package:flutter/…/animation/animation_controller.dart:751
#1      AnimationController.dispose 
package:flutter/…/animation/animation_controller.dart:762
#2      _TyperState._nextAnimation 
package:animated_text_kit/src/typer.dart:190
#3      _rootRun  (dart:async/zone.dart:1122:38)
#4      _CustomZone.run  (dart:async/zone.dart:1023:19)
#5      _CustomZone.runGuarded  (dart:async/zone.dart:925:7)
#6      _CustomZone.bindCallbackGuarded.<anonymous closure>  (dart:async/zone.dart:965:23)
#7      _rootRun  (dart:async/zone.dart:1126:13)
#8      _CustomZone.run  (dart:async/zone.dart:1023:19)
#9      _CustomZone.bindCallback.<anonymous closure>  (dart:async/zone.dart:949:23)
#10     Timer._createTimer.<anonymous closure>  (dart:async-patch/timer_patch.dart:23:15)
#11     _Timer._runTimers  (dart:isolate-patch/timer_impl.dart:384:19)
#12     _Timer._handleMessage  (dart:isolate-patch/timer_impl.dart:418:5)
#13     _RawReceivePortImpl._handleMessage  (dart:isolate-patch/isolate_patch.dart:174:12)
]

Flutter:

• v1.12.13+hotfix.8
• Stable

Dart:

• 2.7.0

[awhitford]

I am seeing a similar issue with a single FadeAnimatedTextKit:

[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: AnimationController.dispose() called more than once.
A given AnimationController cannot be disposed more than once.
The following AnimationController object was disposed multiple times:
  AnimationController#88138(⏭ 1.000; paused; DISPOSED)
#0      AnimationController.dispose.<anonymous closure> (package:flutter/src/animation/animation_controller.dart:751:9)
#1      AnimationController.dispose (package:flutter/src/animation/animation_controller.dart:762:6)
#2      _RotatingTextState._nextAnimation (package:animated_text_kit/src/fade.dart:207:42)
#3      _rootRun (dart:async/zone.dart:1122:38)
#4      _CustomZone.run (dart:async/zone.dart:1023:19)
#5      _CustomZone.runGuarded (dart:async/zone.dart:925:7)
#6      _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:965:23)
#7      _rootRun (dart:async/zone.dart:1126:13)
#8      _CustomZone.run (dart:async/zone.dart:1023:19)
#9      _CustomZone.bindCallback.<anonymous closur<…>

[awhitford]

The problem appears during a screen transition, so the widget's dispose is conflicting with this code in nextAnimation:

    if (_controller != null) _controller.dispose();

    setState(() {});

    _controller = new AnimationController(
      duration: _duration,
      vsync: this,
    );

I recommend refactoring such that the lifecycle of the AnimationController is closely linked to the widget lifecycle. In other words, I would avoid replacing it during nextAnimation -- instead, just reset it or something.

Of course, the simplest solution may be simply to null it after you dispose it. So, replace:

    if (_controller != null) _controller.dispose();

with

    _controller?.dispose();
    _controller = null;

Then, you will need to add a guard to the widget's dispose method too:

   if (null != _controller) {
    _controller
      ..stop()
      ..dispose();
    }

[aadarshadhakalg]

Beside of the TyperAnimatedTextKit widget, have you used any other animation ? I mean have you created your custom animation controller in same file?

[yiminghan]

I'm getting into the same issue. I agree with @awhitford we should just set the controller to null after dispose.

[aagarwal1012]

v2.1.0 of Animated text kit solves this issue, closing this issue for now. Feel free to reopen this issue if any issue arises.

[awhitford]

Code like this:

_controller?.stop();
_controller.dispose();

is a problem and it isn't any better than:

_controller
  ..stop()
  ..dispose();

If _controller is null, then the ?. will protect stop(), but then you will get a Null Pointer Exception calling dispose().

Some are fine (rotate, scale), but some are faulty (colorize, fade).

Also, this code:

if (_controller != null) {	    
  _controller
    ..stop()
    ..dispose();
}

is logically the same:

_controller?.stop();
_controller?.dispose();

The latter is more concise, but arguably less efficient (unless the optimizer can optimize the double ?.).

[niumj]

May be you wrote the source [_controller.dispose();] in the method build.
But Flutter would call build multiple times.So you try to write the code [_controller.dispose();] in the method dispose etc.